At the time of this writing, it is not possible in Flow to restrict access to Workspace through Entity Privileges
because Workspaces are used at a very early stage during routing where the security context is not yet initialized.
As a workaround, we use a Method Privilege which protects this validateWorkspace() method and thus prevents
unauthorized access to a workspace when calling this context's getWorkspace() method.
Since some privilege definitions check the "owner" property of a Workspace, we need a real Workspace object and
not just the name - hence this method.